Decoupled auditory perception from acoustic signal divergence hinders species recognition in territorial poison frogs

Species recognition, encompassing mate and competitor recognition, is an important mechanism for establishing and maintaining species boundaries. The effective communication between a sender and a receiver is crucial for species recognition to occur. In this sense, intraspecific signals are expected to evolve coupled to recognition systems to avoid reproductive interference with other species. Empirical evidence suggests, however, that the asymmetrical evolution of signaling and recognition systems may be widespread in nature. Moreover, the study of recognition systems has classically focused on the perception by females, but the role of males has been largely overlooked. We studied the divergence of acoustic traits and their perception in two nominal species and an intermediate population that form a phenotypic cline in color and body size. We used males’ recognition of and competition with other males as the predicted drivers of the communication system. We found wide and asymmetrical levels of recognition in both species and the intermediate population, which we argue reflects the prevalence of reproductive interference across the system. Significance statement The effective recognition of aggressive signals between males of incipient lineages is expected to prevent costly interactions, such as competing for mates. Therefore, diverging signals should evolve coupled to perceptual systems that allow their recognition. When this process is broken, reproductive interference or the competition between males of distinct lineages for the access to mates will prevail. In our study, we prove that the coupled divergence of acoustic signals and their perception is hindered in incipient lineages of territorial poison frogs ( Phyllobates ). We studied two species and an intermediate population that represent a phenotypic cline in color and body size. Territoriality in poison frogs is widely acknowledged as a predictor of reproductive success in males. Therefore, we argue that males’ auditory perception remained flexible to recognize divergent acoustic traits that could put at risk males’ territory ownership and by extension mate acquisition.